This project is studying in a prospective manner patients who have been successfully resuscitated from out-of-hospital sudden death, in order to characterize the entry event and to develop prognostic indicators of recurrent sudden death in the population. In the first 21 months, 744 emergency cardiac runs have resulted in 65 successful resuscitations. At present 44 patients are being prospectively followed by serial interviews, assessment of clinical status, and 24 hour ECG holter recordings. At present it appears that VPB frequency of greater than 20/hour identifies in part individuals prone to have recurrent sudden death.